Hydralazine (HDZ) is an antihypertensive drug that is a substrate for N-acetyltransferase. Genetically controlled differences in N- acetylation have been implicated in susceptibility to adverse reactions of a number of drugs including HDZ. Slow acetylators are more likely to develop HDZ-induced systemic lupus erythematosus (SLE). The studies proposed in the application are designed to further define the relationship between acetylator phenotype and susceptibility to HDZ-induced SLE. The objectives are: 1) to characterize the pyrmidine adducts formed in vitro by HDZ; 2) to identify the HDZ-DNA adducts formed in mammalian cells; 3) to compare adduct formation in cells from rapid and slow acetylators; 4) to develop an antibody to detect HDZ-DNA adducts; and 5) to compare the metabolism of HDZ in hepatocytes from rapid and slow acetylators. The adducts that are formed by reacting HDZ with pyrimidines will be characterzied by their UV, NMR and mass spectra. Adduct formation will then be evaluated in mammalian cells. Both rabbit and human hepatocytes of both acetylator phenotypes will be used. Monolayer cultures of hepatocytes will be exposed to HDZ. DNA will be isolated, hydrolyzed and identified by spectral comparison and chromatographic retention. Monoclonal antibodies to detect HDZ-DNA adducts will be prepared. The HDZ metabolites formed in monolayer cultures of rapid and slow acetylator rabbit hepatocytes will be examined by GC-MS and HPLC methods.